In 1991, the Government of Portugal created a new department for managing the construction of the new crossing of the Tagus River at Lisbon called GATTEL. The office identified three potential corridors for the new road bridge: eastern (Sacavém-Montijo), central (Chelas-Barreiro), and western (Algés-Trafaria).
The non-governmental organization Grupo de Estudos de Ordenamento de Território e Ambiente (GEOTA) sent an open letter to the prime minister to request more detailed information on this project, in which it defended the central corridor as the best option. The Ministries of Planning, the Environment, Industry, Employment, Defense and Justice; representatives of GATTEL; the municipalities of Almada, Barreiro, Seixal, and Moita, environmental NGOs and experts on transport, territory, and environmental management all supported GEOTA's position.
Even so, on April 25, the eastern corridor (Sacavém-Montijo) was adopted as the definitive option. In October, a decree made the bridge's location official, and the call for tenders and the concession rules were published. The Lusoponte consortium won the bidding process. The government allocated resources of the Community Cohesion Fund to the construction of the bridge, which then implied an Environmental Impact Assessment (EIA). In June, the final EIA report was delivered to GATTEL, which concluded that the negative consequences of this project would be speculation in the affected areas and the acculturation and identity loss of the people living on the south bank of the Tagus River, among others. The new bridge was to pass through a Special Protection Area (SPA) for birds. Even so, the EIA report classified the project as viable.
The public consultation period on the EIA report was opened in July. GEOTA, Liga para a Protecção da Natureza (LPN), Quercus, and the Dom Dinis Institute (IDD) pointed out several flaws in the study and questioned its final conclusion on the project's viability. Public hearings were held. The European Commission opened an investigation into the use of cohesion funds for the construction of the new bridge and to the irregularities denounced in the report by the World Wide Fund for Nature in relation to the failure to comply with the recommendations of the EIA. GEOTA filed a complaint against the Portuguese government for breaches of the European Union’s directives on species and habitat conservation. In December, LPN, Quercus, and IDD presented a similar complaint to the Environment Directorate-General of the European Commission. The complaints were shelved and the use of resources from the Community Fund was approved.
In January 1995, LPN resent a formal complaint, requesting that the European Commission take action. In February, the government proposed the creation of a Construction Monitoring Committee (CMC) that is open to the participation of environmental organizations. The organizations did not accept this invitation. In March, the Supreme Administrative Court dismissed a request filed by the LPN for the annulment of the executive decision to build the new bridge between Sacavém and Montijo. The same month, the final contract for the construction of the bridge was signed and the name of the bridge was announced: the Vasco da Gama Bridge.
Environmental harm was denounced and one infraction proceeding was initiated to Lusoponte. In July, the Portuguese government and the European Commission signed a memorandum of understanding: Portugal pledged to strengthen environmental control measures and Brussels, to release part of the funding.
The environmentalists demanded that the Zona de Proteção Ambiental (ZPE, Special Protected Area) be enlarged to include 400 more hectares and that the powers of the CMC be strengthened. Organizations began to participate in the CMC, which became responsible for coordinating all the entities involved in the monitoring process. On March 29, 1998, the Vasco da Gama Bridge was inaugurated. In April, representatives of the central and local government and local NGOs formed an Observatory on Spatial Planning and Environment.
There are plans to build two more bridges over the Tagus River. The Terceira Travessia do Tejo (TTT, or the Third Tagus Bridge), which will go from Chelas to Barreiro, and the Quarta Travessia do Tejo (QTT, or the Fourth Tagus Bridge), from Algés to Trafaria, are being questioned by the same environmental organizations that intervened in the case of the Vasco de Gama Bridge.